Radioactive isotopes are extensively used for the diagnosis and treatment of various medical conditions. Certain radioactive isotopes have so short a half-life however that they cannot be shipped. Such isotopes are therefore prepared at time of use. One such isotope is the 99m isotope of technetium (99mTc) which is used in many medical procedures such as for the localization of brain tumors. (See Smith, J. Nuc. Med., Vol. 5, p. 871-882, 1964). The 99m isotope of technetium has a half-life of 6 hours and is obtained as the daughter product of molybdenum Mo.sup.99, adsorbed on an alumina column, by elution with saline solution. A suitable column and process for preparing technetium 99m is described in U.S. Pat. No. 3,440,423, issued Apr. 22, 1969. As noted, the radioactive pertechnetate which is obtained is useful in brain scanning or can be converted to other compounds such as labeled technetium sulfide for examination of the liver. Another use, as technetium-labeled albumin, is for placental scanning.
One of the disadvantages of the .sup.99 Mo-99mTc generators as presently known, is that every week a new generator, packed in a bulky load of many pounds of lead inside an expensive packaging case has to be sent to the user.
With these types of generators, Boyd (see IAEE, Vol. I: 3-26, 1973), found that the first few milliliters of eluates contained the major portion of .sup.99 Mo breakthrough, and that since these .sup.99 Mo components can be removed by filtration, he concluded that the .sup.99 Mo is associated with particulate matter arising from the bed, in other words, alumina. This fact suggests, that the .sup.99 Mo found in eluates is still strongly bound to the alumina, and does not break free during elution.
Reese and Mishkin (Am. J. Roentg. 103: 896, 1968) and Lo, et al. (Radiology 93: 1198-1199, 1969) found that the use of tandem generators resulted in a lesser leakage of .sup.99 Mo., probably because of the filtration-like function for particulate material of the second generator or maybe, because the .sup.99 Mo in solution, if any, was reabsorbed.